CN111599814A - Split-gate flash memory and forming method thereof - Google Patents
Split-gate flash memory and forming method thereof Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 38
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims abstract description 164
- 229920005591 polysilicon Polymers 0.000 claims abstract description 86
- 230000005641 tunneling Effects 0.000 claims abstract description 24
- 238000005530 etching Methods 0.000 claims abstract description 22
- 239000000758 substrate Substances 0.000 claims description 24
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 claims description 7
- UORVGPXVDQYIDP-UHFFFAOYSA-N borane Chemical compound B UORVGPXVDQYIDP-UHFFFAOYSA-N 0.000 claims description 6
- 239000002019 doping agent Substances 0.000 claims description 5
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 4
- 230000007423 decrease Effects 0.000 claims description 4
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 claims description 3
- 229910000085 borane Inorganic materials 0.000 claims description 3
- MROCJMGDEKINLD-UHFFFAOYSA-N dichlorosilane Chemical compound Cl[SiH2]Cl MROCJMGDEKINLD-UHFFFAOYSA-N 0.000 claims description 3
- 239000005049 silicon tetrachloride Substances 0.000 claims description 3
- 229910000073 phosphorus hydride Inorganic materials 0.000 claims description 2
- 239000005052 trichlorosilane Substances 0.000 claims description 2
- 230000003247 decreasing effect Effects 0.000 claims 1
- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 claims 1
- 150000002500 ions Chemical class 0.000 abstract description 11
- 238000002347 injection Methods 0.000 abstract description 10
- 239000007924 injection Substances 0.000 abstract description 10
- 230000009286 beneficial effect Effects 0.000 abstract description 5
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- 230000008021 deposition Effects 0.000 description 4
- 238000005468 ion implantation Methods 0.000 description 4
- 238000005229 chemical vapour deposition Methods 0.000 description 3
- 239000005046 Chlorosilane Substances 0.000 description 2
- 239000005922 Phosphane Substances 0.000 description 2
- KOPOQZFJUQMUML-UHFFFAOYSA-N chlorosilane Chemical compound Cl[SiH3] KOPOQZFJUQMUML-UHFFFAOYSA-N 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910000064 phosphane Inorganic materials 0.000 description 2
- 239000012495 reaction gas Substances 0.000 description 2
- 125000006850 spacer group Chemical group 0.000 description 2
- PPDADIYYMSXQJK-UHFFFAOYSA-N trichlorosilicon Chemical compound Cl[Si](Cl)Cl PPDADIYYMSXQJK-UHFFFAOYSA-N 0.000 description 2
- ZXNQLIVFWAFRKQ-UHFFFAOYSA-N [B].CC Chemical compound [B].CC ZXNQLIVFWAFRKQ-UHFFFAOYSA-N 0.000 description 1
- RBFQJDQYXXHULB-UHFFFAOYSA-N arsane Chemical compound [AsH3] RBFQJDQYXXHULB-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- SLLGVCUQYRMELA-UHFFFAOYSA-N chlorosilicon Chemical compound Cl[Si] SLLGVCUQYRMELA-UHFFFAOYSA-N 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000002784 hot electron Substances 0.000 description 1
- 238000002513 implantation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
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- 229910000077 silane Inorganic materials 0.000 description 1
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- H10B—ELECTRONIC MEMORY DEVICES
- H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
- H10B41/30—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by the memory core region
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
- H10B41/60—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates the control gate being a doped region, e.g. single-poly memory cell
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Abstract
The invention provides a split-gate flash memory and a forming method thereof.A polycrystalline silicon layer grows on a tunneling oxide layer and is doped in the polycrystalline silicon layer; the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is smaller than that of the bottom of the polycrystalline silicon layer; and etching the polysilicon layer to form a word line layer. The etching rate of the polycrystalline silicon layer is positively correlated with the doping concentration of the polycrystalline silicon layer, the top of the polycrystalline silicon layer is not doped or has smaller doping concentration, so that the top of the polycrystalline silicon layer has lower etching rate, which is beneficial to the improvement of the depression height, thereby increasing the thickness of a formed word line layer. The thickness of the word line layer is increased, so that the problem of programming crosstalk failure of the split-gate flash memory is effectively solved; meanwhile, the thickness of the word line layer is increased, source and drain ions cannot penetrate through the word line layer during injection, and a process window of source and drain ion injection is enlarged.
Description
Technical Field
The invention belongs to the technical field of integrated circuit manufacturing, and particularly relates to a split-gate flash memory and a forming method thereof.
Background
Flash memory includes two basic structures: gate stack (stack gate) and split gate (split gate) devices. The split-gate device forms a word line serving as an erasing gate on one side of the floating gate, the word line serves as a selection gate, in erasing and writing performance, the split-gate device effectively avoids the over-erasing effect of the stacked-gate device, and the circuit design is relatively simple. And the split gate structure utilizes source end hot electron injection to program, has higher programming efficiency, and is widely applied to various electronic products such as intelligent cards, SIM cards, microcontrollers, mobile phones and the like.
In the split-gate flash memory, the thickness and the width of the word line polycrystalline silicon layer influence the anti-interference performance of the split-gate flash memory, and the width of the word line polycrystalline silicon layer is closely related to the thickness of the word line polycrystalline silicon layer. If the thickness of the word line polysilicon layer is too thin, the split gate flash memory can be caused to have programming crosstalk failure, such as column punch-through crosstalk failure (column punch-through crosstalk).
In an actual process, the edge of a wafer of a split-gate flash memory is randomly subjected to programming crosstalk failure, a failure sample is shown in fig. 1, a word line layer 01 is formed by etching a polycrystalline silicon layer, the top profile of the word line layer 01 is provided with a depression a, the failure sample shows a lower depression a, the lower the depression a is, the thinner the thickness of the word line layer 01 is, if the word line layer 01 is too thin, the threshold voltage of the word line layer is reduced, and meanwhile, source and drain ions penetrate through the word line layer 01 during injection; and the thickness of the word line layer affects the anti-interference performance of the flash memory. The thickness of the word line 01 is too thin, which easily causes the problem of programming crosstalk failure of the split-gate flash memory.
Disclosure of Invention
The invention aims to provide a split-gate flash memory and a forming method thereof, which solve the problem of programming crosstalk failure of the split-gate flash memory and simultaneously increase a process window of source-drain ion implantation.
The invention provides a forming method of a split-gate flash memory, which comprises the following steps:
providing a substrate, and forming a tunneling oxide layer on the substrate;
growing a polysilicon layer on the tunneling oxide layer and doping in the polysilicon layer; the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is smaller than that of the bottom of the polycrystalline silicon layer; and
and etching the polysilicon layer to form a word line layer.
Furthermore, in the thickness direction, the doping concentration of the polysilicon layer is gradually reduced from the side close to the tunneling oxide layer to the side far away from the tunneling oxide layer.
Furthermore, the polycrystalline silicon layer is grown in a primary furnace tube, and the concentration of the doping gas is gradually reduced in the process of growing the polycrystalline silicon layer.
Further, the polycrystalline silicon layer is formed by segmented growth in the furnace tube for N times in sequence, the polycrystalline silicon layer with the first thickness is formed in the furnace tube for the first time, the polycrystalline silicon layer with the second thickness is formed in the furnace tube for the second time, and the like, and the polycrystalline silicon layer with the Nth thickness is formed in the furnace tube for the Nth time; the concentration of the doping gas in the first furnace tube to the Nth furnace tube is gradually reduced, and the concentration of the doping gas in the Nth furnace tube is the lowest or is not doped; the sum of the first thickness, the second thickness to the Nth thickness is equal to the total thickness of the polysilicon layer.
Further, the reactive gas source for growing the polysilicon layer comprises: any one or combination of more than two of the group consisting of monosilane, dichlorosilane, trichlorosilane and silicon tetrachloride.
Further, the doping gas comprises phosphane or borane.
Further, the polysilicon layer is doped with N-type or P-type.
The present invention also provides a split gate flash memory, comprising:
a substrate;
a tunneling oxide layer on the substrate;
and the word line layer is positioned on the tunneling oxide layer and is formed by doping a polycrystalline silicon layer, the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is less than that of the bottom of the polycrystalline silicon layer.
Furthermore, in the thickness direction, the doping concentration of the polysilicon layer is gradually reduced from the side close to the tunneling oxide layer to the side far away from the tunneling oxide layer.
Furthermore, a source line layer and a floating gate oxide layer are arranged on the substrate, a floating gate polycrystalline silicon layer is deposited on the surface of the floating gate oxide layer, a first side wall is arranged between the source line layer and the word line layer, and a second side wall is arranged between the source line layer and the floating gate oxide layer and the floating gate polycrystalline silicon layer.
Compared with the prior art, the invention has the following beneficial effects:
in the split-gate flash memory and the forming method thereof provided by the invention, a polycrystalline silicon layer grows on the tunneling oxide layer and is doped; the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is smaller than that of the bottom of the polycrystalline silicon layer; and etching the polysilicon layer to form a word line layer. The etching rate of the polycrystalline silicon layer is positively correlated with the doping concentration of the polycrystalline silicon layer, the top of the polycrystalline silicon layer is not doped or has smaller doping concentration, so that the top of the polycrystalline silicon layer has lower etching rate, which is beneficial to the improvement of the depression height, thereby increasing the thickness of a formed word line layer. The thickness of the word line layer is increased, so that the problem of programming crosstalk failure of the split-gate flash memory is effectively solved; meanwhile, the thickness of the word line layer is increased, source and drain ions cannot penetrate through the word line layer during injection, and a process window of source and drain ion injection is enlarged.
Drawings
FIG. 1 is a top-down recess of a word line layer of a split-gate flash memory.
Fig. 2 is a flow chart illustrating a method for forming a split-gate flash memory according to an embodiment of the invention.
Fig. 3 to 8 are schematic diagrams illustrating steps of a method for forming a split-gate flash memory according to an embodiment of the invention.
Wherein the reference numbers are as follows:
11-a substrate; 111-source region 12-source line layer; 13-floating gate oxide layer; 14-floating gate polysilicon layer; 15-a first side wall; 16-a second side wall; 17-tunneling oxide layer; 18-a polysilicon layer; 18' -a wordline layer; 19-a polysilicon layer; 20-a polysilicon layer; 21-word line sidewalls; 22-drain region.
Detailed Description
Based on the above research, the embodiment of the invention provides a split-gate flash memory and a forming method thereof. The invention is described in further detail below with reference to the figures and specific examples. The advantages and features of the present invention will become more apparent from the following description. It is to be noted, however, that the drawings are designed in a simplified form and are not to scale, but rather are to be construed in an illustrative and descriptive sense only and not for purposes of limitation.
An embodiment of the present invention provides a method for forming a split-gate flash memory, as shown in fig. 2, including:
providing a substrate, and forming a tunneling oxide layer on the substrate;
growing a polysilicon layer on the tunneling oxide layer and doping in the polysilicon layer; the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is smaller than that of the bottom of the polycrystalline silicon layer; and
and etching the polysilicon layer to form a word line layer.
The method for forming the split-gate flash memory according to the embodiment of the invention is described in detail below with reference to fig. 3 to 8.
As shown in fig. 3, a substrate 11 is provided, and a tunnel oxide layer 17 is formed on the substrate 11. Specifically, an active line layer 12 and a floating gate oxide layer 13 are further formed on the substrate, the active line layer 12 is located above the active region 111, a floating gate polysilicon layer 14 is deposited on the surface of the floating gate oxide layer 13, a floating gate tip is arranged on the floating gate polysilicon layer 14, and the floating gate tip is in contact with the tunneling oxide layer 17. And a second side wall 16 is arranged between the source line layer 12 and the floating gate oxide layer 13 and the floating gate polysilicon layer 14, and the source line layer 12 is isolated from the floating gate oxide layer 13 and the floating gate polysilicon layer 14 by the second side wall 16. A first sidewall 15 is further formed above the substrate 11, and the first sidewall 15 is located on both sides of the source line layer 12 and on the surface of the floating gate polysilicon layer 14. The tunnel oxide layer 17 covers the surface of the substrate 11, the side of the floating gate polysilicon layer 14, the surface of the second sidewall 15, and the surface of the source line layer 12.
As shown in fig. 4, a polysilicon layer 18 is grown on the tunnel oxide layer 17 and doped in the polysilicon layer 18; the top of the polysilicon layer 18 is undoped, or, in the thickness direction, the doping concentration of the top of the polysilicon layer 18 is smaller than the doping concentration of the bottom of the polysilicon layer 18.
In the thickness direction, the doping concentration of the polysilicon layer 18 may gradually decrease from the side close to the tunnel oxide layer 17 to the side far from the tunnel oxide layer 17.
In the thickness direction, from the side close to the tunnel oxide layer 17 to the side far from the tunnel oxide layer 17, the doping concentration of the polysilicon layer 18 may also decrease in a stepwise manner, for example, the doping concentration at the top of the polysilicon layer 18 is a first constant doping concentration, the doping concentration at the bottom of the polysilicon layer 18 is a second constant doping concentration, and the first constant doping concentration is smaller than the second constant doping concentration.
The polycrystalline silicon layer can be formed by growing in a primary furnace tube, and the concentration of the doping gas is gradually reduced in the process of growing the polycrystalline silicon layer. In the thickness direction, the doping concentration of the generated polysilicon layer 18 gradually decreases from the side close to the tunnel oxide layer 17 to the side far from the tunnel oxide layer 17.
The polycrystalline silicon layer is formed by segmented growth in the furnace tube for N times in sequence, the polycrystalline silicon layer with the first thickness is formed in the furnace tube for the first time, the polycrystalline silicon layer with the second thickness is formed in the furnace tube for the second time, and so on, and the polycrystalline silicon layer with the Nth thickness is formed in the furnace tube for the Nth time; the concentration of the doping gas in the first furnace tube to the Nth furnace tube is gradually reduced, and the concentration of the doping gas in the Nth furnace tube is the lowest or is not doped; the sum of the first thickness, the second thickness to the Nth thickness is equal to the total thickness of the polysilicon layer. When the concentration of the doping gas in the furnace tube is constant each time, the doping concentration of the polysilicon layer 18 is reduced in a stepwise manner from the side close to the tunnel oxide layer 17 to the side far from the tunnel oxide layer 17 in the thickness direction.
When the concentration of the doping gas in the furnace tube is gradually reduced each time, the doping concentration of the polysilicon layer 18 is gradually reduced from the side close to the tunnel oxide layer 17 to the side far from the tunnel oxide layer 17 in the thickness direction.
The top of the polysilicon layer is undoped, or the doping concentration of the top of the polysilicon layer is less than the doping concentration of the bottom of the polysilicon layer in the thickness direction. As shown in fig. 5, the top 19b of the polysilicon layer is undoped, which is understood to mean that the doping concentration of the top 19b of the polysilicon layer is zero, and the doping concentration of the top 19b of the polysilicon layer is less than the doping concentration of the bottom 19a of the polysilicon layer in the thickness direction.
As shown in fig. 6, the doping concentration of the top 20b of the polysilicon layer is smaller than that of the bottom 20a of the polysilicon layer in the thickness direction.
In conventional processes, polysilicon layer deposition uses a constant doping concentration in the furnace tool. The word line layer formed by the polysilicon layer has the same doping concentration from bottom to top, so that the word line layer has the same etching rate from top to bottom in the step of etching the word line layer to form the word line.
In the embodiment, a polysilicon layer is grown on the tunneling oxide layer and doped in the polysilicon layer; the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is smaller than that of the bottom of the polycrystalline silicon layer; and etching the polysilicon layer to form a word line layer. The etching rate of the polycrystalline silicon layer is positively correlated with the doping concentration of the polycrystalline silicon layer, the top of the polycrystalline silicon layer is not doped or has smaller doping concentration, so that the top of the polycrystalline silicon layer has lower etching rate, which is beneficial to the improvement of the depression height, thereby increasing the thickness of a formed word line layer. The thickness of the word line layer is increased, and the problem of programming crosstalk failure of the split-gate flash memory is effectively solved.
A polysilicon layer 18 is grown on the tunnel oxide layer 17 and doped in the polysilicon layer 18. Specifically, a semiconductor wafer of a split-gate flash memory is placed in a reaction chamber, and the split-gate flash memory comprises a substrate 11 on which a tunnel oxide layer 17 is formed. The reaction chamber may be a furnace-type reaction chamber or a single wafer reaction furnace. Placing the substrate 11 in a reaction chamber; introducing a group of gas sources into the reaction chamber; a chemical vapor deposition process step is performed, the set of gas sources including a reactive gas source, a dopant gas source, and a catalyst gas source. The doping gas comprises phosphane or borane.
The polycrystalline silicon layer is doped in an N type or a P type. The resistivity of the polysilicon is reduced by doping, and the conductivity of the polysilicon layer is improved. And doping impurities while performing a polysilicon deposition reaction. The impurities may be driven in by means of ion implantation or by means of high temperature diffusion. Taking N-type doping as an example, the N-type doped polysilicon layer is formed by N-type doping, and the doped ions are, for example, phosphorus ions.
And introducing a reaction gas source, doping gas and a catalyst into the reaction chamber. The reactive gas source is, for example, a silane-based or chlorosilane-containing gas including monosilane (SiH)4) Dichlorosilane (SiH)2Cl2) Silicon trichloride (SiHCl)3) With silicon tetrachloride (SiCl)4) Any one or a combination of two or more of them.
The N-type dopant gas is, for example, Phosphine (PH)3) Or arsine (AsH)3). The catalyst is, for example, an agent that enhances the deposition rate of polysilicon, including boron ethane (B)2H6) And the like. Then, a chemical vapor deposition process step is carried out to form the N-type doped polysilicon.
In the above process, since a catalyst is added to the reaction chamber to increase the deposition rate of polysilicon, chlorosilane-containing gas can be used as a reaction gas source for chemical vapor deposition of polysilicon to increase the selectivity of the gas on the process.
As shown in fig. 7, the polysilicon layer 18 is etched to form a word line layer 18', the etching rate of the polysilicon layer is positively correlated to the doping concentration of the polysilicon layer, the polysilicon layer with higher doping concentration has higher etching rate, and the doping concentration of the top of the polysilicon layer is less than the doping concentration of the bottom of the polysilicon layer. The bottom of the polycrystalline silicon layer has a high etching rate, and the top of the polycrystalline silicon layer has a low etching rate, so that the improvement of the depression height is facilitated, the top profile of the word line layer is gentle, and the thickness of the formed word line layer is increased. The thickness of the word line layer is increased, so that the problem of programming crosstalk failure of the split-gate flash memory is effectively solved; meanwhile, the thickness of the word line layer is increased, source and drain ions cannot penetrate through the word line layer during injection, and a process window of source and drain ion injection is enlarged. The doping concentration difference distribution in the thickness direction of the polycrystalline silicon layer is tested, and the method has no influence on the performance and the cost of the split-gate flash memory.
Next, as shown in fig. 8, word line spacers 21 are formed on one side of the word line layer word lines 18', and drain regions 22 are formed on both sides of the word line spacers 21 by ion implantation. The thickness of word line layer 18 'is increased so that source and drain ions will not penetrate word line layer 18' during implantation, increasing the process window for source and drain ion implantation. The word lines 18 'have first sidewalls 15 on one side and word line sidewalls 21 on the other side, the first sidewalls 15 separating the source line layer 12 from the word line layer 18'.
The present embodiment further provides a split gate flash memory, including:
a substrate;
a tunneling oxide layer on the substrate;
and the word line layer is positioned on the tunneling oxide layer and is formed by doping a polycrystalline silicon layer, the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is less than that of the bottom of the polycrystalline silicon layer.
In the thickness direction, the doping concentration of the polycrystalline silicon layer is gradually reduced from the side close to the tunneling oxide layer to the side far away from the tunneling oxide layer.
The floating gate structure comprises a substrate, and is characterized in that a source line layer and a floating gate oxide layer are arranged on the substrate, a floating gate polycrystalline silicon layer is deposited on the surface of the floating gate oxide layer, a first side wall is arranged between the source line layer and a word line layer, and a second side wall is arranged between the source line layer and the floating gate oxide layer and the floating gate polycrystalline silicon layer. And a floating gate tip is arranged on the floating gate polycrystalline silicon layer and is contacted with the tunneling oxide layer.
In summary, the present invention provides a split-gate flash memory and a method for forming the same, wherein a polysilicon layer is grown on the tunneling oxide layer and doped in the polysilicon layer; the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is smaller than that of the bottom of the polycrystalline silicon layer; and etching the polysilicon layer to form a word line layer. The etching rate of the polycrystalline silicon layer is positively correlated with the doping concentration of the polycrystalline silicon layer, the top of the polycrystalline silicon layer is not doped or has smaller doping concentration, so that the top of the polycrystalline silicon layer has lower etching rate, which is beneficial to the improvement of the depression height, thereby increasing the thickness of a formed word line layer. The thickness of the word line layer is increased, so that the problem of programming crosstalk failure of the split-gate flash memory is effectively solved; meanwhile, the thickness of the word line layer is increased, source and drain ions cannot penetrate through the word line layer during injection, and a process window of source and drain ion injection is enlarged.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the method disclosed by the embodiment, the description is relatively simple because the method corresponds to the device disclosed by the embodiment, and the relevant points can be referred to the description of the method part.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.
Claims (10)
1. A method for forming a split-gate flash memory is characterized by comprising the following steps:
providing a substrate, and forming a tunneling oxide layer on the substrate;
growing a polysilicon layer on the tunneling oxide layer and doping in the polysilicon layer; the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is smaller than that of the bottom of the polycrystalline silicon layer; and
and etching the polysilicon layer to form a word line layer.
2. The method of claim 1, wherein the doping concentration of the polysilicon layer is gradually or stepwise decreased from a side close to the tunnel oxide layer to a side far from the tunnel oxide layer in a thickness direction.
3. The method of claim 1, wherein the polysilicon layer is grown in a furnace, and the concentration of the dopant gas is gradually reduced during the growth of the polysilicon layer.
4. The method of claim 1, wherein the polysilicon layer is formed by segmented growth in N furnace tubes, the first furnace tube forms a polysilicon layer with a first thickness, the second furnace tube forms a polysilicon layer with a second thickness, and so on, the Nth furnace tube forms a polysilicon layer with an Nth thickness; the concentration of the doping gas in the first furnace tube to the Nth furnace tube is gradually reduced, and the concentration of the doping gas in the Nth furnace tube is the lowest or is not doped; the sum of the first thickness, the second thickness to the Nth thickness is equal to the total thickness of the polysilicon layer.
5. The method as claimed in any one of claims 1 to 4, wherein the reactive gas source for growing the polysilicon layer comprises: any one or combination of more than two of the group consisting of monosilane, dichlorosilane, trichlorosilane and silicon tetrachloride.
6. The method as claimed in any one of claims 1 to 4, wherein the dopant gas comprises phosphine or borane.
7. The method as claimed in any one of claims 1 to 4, wherein the polysilicon layer is doped with N-type or P-type dopant.
8. A split-gate flash memory, comprising:
a substrate;
a tunneling oxide layer on the substrate;
and the word line layer is positioned on the tunneling oxide layer and is formed by doping a polycrystalline silicon layer, the top of the polycrystalline silicon layer is not doped, or in the thickness direction, the doping concentration of the top of the polycrystalline silicon layer is less than that of the bottom of the polycrystalline silicon layer.
9. The split-gate flash memory of claim 8, wherein the doping concentration of the polysilicon layer gradually decreases from a side close to the tunnel oxide layer to a side far from the tunnel oxide layer in a thickness direction.
10. The split-gate flash memory according to claim 8 or 9, wherein a source line layer and a floating gate oxide layer are disposed on the substrate, a floating gate polysilicon layer is deposited on the surface of the floating gate oxide layer, a first sidewall is disposed between the source line layer and the word line layer, and a second sidewall is disposed between the source line layer and the floating gate oxide layer and the floating gate polysilicon layer.
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CN107331666A (en) * | 2017-07-05 | 2017-11-07 | 上海华虹宏力半导体制造有限公司 | Split-gate flash memory and the method for avoiding its programming interference from failing |
CN110534515A (en) * | 2018-05-24 | 2019-12-03 | 长鑫存储技术有限公司 | Reduce the manufacturing method and semiconductor memory of unit contact deficiency |
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US20040188749A1 (en) * | 2003-03-27 | 2004-09-30 | Taiwan Semiconductor Manufacturing Co., Ltd. | Method for forming a box shaped polygate |
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